1. Field of the Invention
The present invention relates to a coupling structure for a pair of members at least one of which is a resin molding member and a coupling method thereof.
2. Description of the Prior Art
The coupling structure and the coupling method to be herein referred to will be illustrated below with reference to exterior parts such as an exterior cover of a camera and a transparent plate to be coupled therewith.
As shown in FIG. 30, on a front cover 34 of a camera there are provided a lens cover window 35, a view finder objective window 36, a flashing section window 37 of an electronic flash unit, etc., with which the respectively designated molded members are coupled. As to their coupling structure there exist several coupling methods shown in FIGS. 31(a) to 31(d) with respect to the lens cover window 35.
Firstly, one of those structures is, as shown in FIG. 31(a), a coupling structure by integration of parts in insert molding. That is to say, on the whole periphery of a transparent plate 38 as an assembling part of an undercut is provided, and with the transparent plate 38 held in a die, resin is poured therearound to form a front cover 34, thereby coupling the front cover 34 with the transparent plate 38.
Secondly, there is a structure as shown in FIG. 31(b) made by applying an adhesive 39 to the whole periphery of the transparent plate 38 so that the front cover 34 can be integrated with the transparent plate 38.
Third, there is a thermal fusing coupling structure of applying a supersonic wave to the engaging part between the transparent plate 38 and the front cover 34, thereby partially fusing the peripheral part thereof.
Now, in the case of water-proof cameras, with respect to the relation between the front cover 34 and the transparent plate 38 as above, it is required not merely to couple two things together but also to couple them so as to produce a water-proof effect to the coupled product. To this end, the application of an adhesive in FIG. 31(b) or the thermal fusing in FIG. 31(c) is normally provided over the whole periphery of the coupling part. From the view point of waterproofing as above, there may be given a structure to use packings 40, 41 as in FIG. 31(d). In this structure, the front cover 34 and an auxiliary cover 42 are respectively provided with recesses, and, with packings 40, 41 fitted into these recesses, the front cover 34 and the auxiliary cover 42 are coupled together in an appropriate method.
However, the aforementioned structures FIGS. 31(b) and 31(d) have disadvantages in requiring subsidiary materials such as adhesives, packings (sealing material), involving extremely poor efficiency of assembling work. The structure (c) necessitates a fusing process of applying a separate energy of heat to a resin molding product. Moreover, these coupling structures FIGS. 31(b), (c), and 31(d) cannot be realized before preparing in advance the two molding materials to be coupled. As to the coupling structure FIG. 31(a), although coupling is performed in a die for molding one of the molding materials, it is by all means necessary as its premise to prepare the assembling part.
As reviewed above, conventional coupling structures have had drawbacks in requiring many assembling steps and subsidiary materials and in automatization of assembling work and curtailment of part items. Moreover, since the highest strength is obtained in, for example, the structure FIG. 31(a) when the wall thickness L.sub.1 of the undercut part is selected to be 1/3 of the whole wall thickness t (ref. FIG. 32), particularly in the case of a generally thin-type member, the undercut part has to be made extremely thin, with the result that it has insufficient strength.